This invention is related to balloon catheters.
Heretofore, balloon catheters have been used, for example, for the percutaneous transluminal coronary angioplasty or PTCA. One such balloon catheter comprises of a thin flexible shaft and a balloon disposed on the distal end of the shaft. When fluid is supplied to or removed from the proximal end of the shaft via a supply/removal path for liquid, the balloon on the distal end of the shaft inflates or contracts.
In general, the shaft of the balloon catheter has high flexibility. High flexibility ensures that the shaft can flexibly curve along a bending blood vessel to smoothly guiding the balloon catheter into the vessel. But having a shaft with high flexibility naturally lacks rigidity and therefore provides poor pushability in the operation of the balloon catheter.
To improve on the above mention problem a balloon catheter having a core made of metal wire or the like fixed inside the shaft was provided. Since such a balloon catheter had a higher rigidity due to its core, the pushability in the operation of the balloon catheter was improved compared to a balloon catheter without a core. However, to some extent the flexibility of the shaft was sacrificed due to the more rigid core.
In the case of a conventional balloon catheter, though either one of flexibility or pushability was alternatively improved depending on whether the shaft of balloon catheter had a core or not, another important property is sacrificed. Once either type of a balloon catheter is chosen adjusting for flexibility or pushability during the operation of the balloon catheter that corresponds to encountered circumstances is impossible.
Wherefore, an object of the present invention is to provide a balloon catheter whose flexibility or pushability can be controlled depending on encountered circumstances during its operation.
In order to achieve the above and other objects, the present invention provides a balloon catheter having a thin and flexible shaft in which a fluid supply/removal path extends from the proximal end to the distal end. To the distal end of the shaft a balloon is secured. The balloon is inflated when fluid is supplied into its inside via the fluid supply/removal path, and is contracted when the fluid in its inside is removed. Finally, a core is provided in such a way that the core is inserted into the shaft from the proximal end of the shaft into its inside, and is slidable along the shaft. It is to be appreciated that allowing the tip end of the core to protrude from the shaft is prevented.
For the balloon catheter of the present invention, its structure and material are the same as those for a conventional balloon catheter. Typically, the balloon is made of a moldable polymer like, for example, polyurethane, latex, silicone rubber, natural rubber, polyvinyl chloride, polyamide, polyamide elastomer, copolymer of ethylene and vinyl acetate, polyethylene, polyimide, polyethylene terephthalate, fluorine resin and the like. However, it is to be appreciated that any other resin which is flexibly extendable and shrinkable, and is harmless as a medical apparatus can also be used, as there is no special limitation on such useable materials. Additionally, the shaft may be made of any material similar to that of the balloon so long as the material used can be flexibly bent while maintaining the form of the lumen.
To increase rigidity, the shaft has an insertable core. This core is made of a material which increases rigidity of the shaft without sacrificing for the lowest flexibility demanded of the shaft. Specifically, a metal wire thinner than the shaft or the like is used. Preferably, the metal wire has sufficient rigidity, even though very thin, and such tenacity that it does not break when bent. More specifically, such a metal used includes stainless steel, tungsten, nickel- titanium alloy, amorphous alloy and the like.
The core of the present invention is arranged in such a way that its end cannot protrude to the outside of the shaft. Various arrangement structures can be applied. For example, while a receiving space for a core is kept in the shaft, the length of the core insertable into the shaft is made shorter than the length of the receiving space. Such a structure prevents the core from protruding outside of the shaft. Since the end part of the core cannot protrude to the outside of the receiving space, the distal end of the receiving space may be of any structure. Alternatively, by applying a structure in which the end part of the core abuts the distal end of a wall defining the receiving space, the end part of the core is prevented from being protruded to the outside of the shaft. In this alternative embodiment the distal end of the wall defining the receiving space should be formed in such a way to prevent problems from occurring should the core abut the distal end of the wall. Further, in this alternative embodiment the core is not restricted concerning its total length and can be made, for example, excessively long, since the core cannot be further pushed into the receiving space, once the end part of the core abuts the distal end of the wall.
Though either a gas or liquid can be used as the fluid for inflating the balloon, liquid is more preferable because of the lesser effect pressure has on changing the volume of an inflated balloon. Such a liquid includes a physiological salt solution, a solution containing contrast medium or the like. In the case of gas, an inactive gas like helium is preferable.
When using the present invention, for example, when the stenosed part of the blood vessel is to be expanded with a catheter, the balloon catheter is inserted into the blood vessel in the same manner as a conventional balloon catheter. The difference being the slidable core of the catheter, which when slid towards the distal end, provides a higher rigidity to its influenced part of the shaft, while the uninfluenced part remains more flexible. Conversely, when the core is slid towards the proximal end, the part of the shaft without the core""s influence becomes more flexible, while the part of the shaft with the core remains less flexible. Therefore, the flexibility and the pushability of the balloon catheter of the invention can be adjusted depending on the circumstances encountered when in use.
Specifically, in the circumstance where there is a bend in a blood vessel with the present invention an adjustment can be performed where the core is slid to the distal end side to keep good pushability until the catheter reaches the bent part of the blood vessel. Once at the bend, the core is then slid to the proximal end side in order to improve the flexibility of the distal end part of the shaft so that the catheter may pass through the bent part of the blood vessel. In this manner, the balloon catheter of the present invention makes its possible to adjust for flexibility or pushability during its operation to correspond to encountered circumstances.
The body conformation, the state of bending of the blood vessel and the distance from the insert portion of the catheter to the lesion of the patient differ depending on the patient to whom a balloon catheter is applied. By sliding the core corresponding to these conditions, the length of the shaft with high flexibility can be freely adjusted.
Moreover, as for the balloon catheter of the present invention, the core is preferably exchangeably formed by pulling out the core from the shaft. According to the balloon catheter formed in such a way, the rigidity of the shaft can be finely adjusted if only a few kinds of core are prepared, since the core can be pulled out from the shaft and exchanged. Needless to say, when fine adjustment of the rigidity of the shaft is unnecessary, the catheter may be formed in such a way that the core cannot be pulled out from the shaft or cannot be exchanged even if it can be pulled out (for example, a structure in which it is difficult for the core to be reinserted once it has been pulled out). Adopting a structure where the core cannot be pulled out from the shaft would avoid the trouble caused by a core being pulled by mistake.
The balloon catheter according to a further aspect of the invention has a structure in which the core or a part secured to the core can be secured to the shaft or to a part secured to the shaft.
Examples of a part secured to the core include a kind of knob secured to the core for easier insertion of the core, a stopper for preventing excessive insertion of the core by abutting the inlet of the shaft once the core is inserted by a predetermined length, and the like. The original usage of these parts is not especially limited. Needless to say, some other specific part may be used to secure the core to the shaft.
For a part secured to the shaft, examples include a securing piece for securing the shaft to the body of the patient or a connector fixed on the proximal end of the shaft. The original usage of these parts is not especially limited. Needless to say, some other specific part may be used to secure the shaft to the core.
According to the balloon catheter of the present invention, by securing the core or the part secured to the core (these will be called a xe2x80x9ccore side partxe2x80x9dhereafter) to the shaft or the part secured to the shaft (these will be called a xe2x80x9cshaft side partxe2x80x9d, hereafter), any relative displacement between the core and the shaft can be prevented from occurring. Therefore, effectively preventing the trouble associated with displacing the core relative to the shaft, thus effecting the portion of higher rigidity in part of the shaft, to an unexpected length during the insertion of the catheter.
As for the balloon catheter, any structure can be adopted even if the structure is formed in such a way that the securing of the core side part to the shaft side part is performed after the relative position of both parts has been determined. For example, a securing mechanism may be adopted in which the core side part and the shaft side part provided with a protrusion and a recess, respectively (or a recess and a protrusion, respectively) are engaged with each other, accompanied by elastic deformations. Alternatively, the core side part may be fixed to the shaft side part by means of a screw or the like, or the deviation between both parts may be prevented from occurring by the friction between the core side part and the shaft side part. Also, a structure can be adopted in which the relative position of the core side part and the shaft side part is continuously changed and they can be secured at any position. Furthermore, the structure may be such that both parts can be secured only when the relative position of the core side part and the shaft side part is changed to either of previously determined multiple positions.
The balloon catheter according to yet another aspect of the invention where the core is insertable into the fluid supply/removal path.
According to the balloon catheter with such a structure, the fluid supply/removal path used for supplying fluid to the balloon is also used as the space for housing the core. Therefore, the shaft can be thinner than a balloon catheter provided separately with a fluid supply/removal path and a housing space for a core. As a result, the catheter can be applied to thinner blood vessels, and to larger blood vessel in order to interrupt less of the blood flow when inserted.
The balloon catheter according to another aspect of the invention is provided with a connector which is disposed between the fluid supply source and the proximal end of the shaft connecting them together.
There are formed inside the connector a first passage connecting the fluid supply/removal path and the fluid supply source, and a second passage connecting the fluid supply/removal path and a core-inserting port into which the core can be inserted. Further, a closing part is provided inside the connector. The closing part can close the second passage to prevent fluid from flowing out from the second passage.
According to the balloon catheter formed in the above mentioned manner, the core is inserted through the core-inserting port and guided to the fluid supply/removal path via the second passage, while the fluid supplied from the fluid supply source flows into the fluid supply/removal path via the first passage. The first and second passages are both connected with the fluid supply/removal path. Therefore, the fluid flowing into the first passage also flows into the second passage, though the second passage can be closed with the closing part. Accordingly, the fluid is prevented from flowing out from the second passage, if the second passage is only closed with the closing part.
In the balloon catheter according to a further aspect of the invention, the closing part closes the second passage by abutting the outer periphery of the core with the core being inserted into the second passage, while the core is secured to the connector.
According to the balloon catheter formed in such a structure, there is no need to remove the core beforehand when the second passage is closed with the closing part. In addition, the whole structure can be made more compact, since no special parts are needed for securing the core side part to the shaft side part.
Though the structure of the catheter of the invention has been described before in detail, in addition to the aforementioned structure characteristic to the invention, any known structure adopted in such a kind of balloon catheter can be properly adopted.
Among such balloon catheters, for example, a catheter of so-called single lumen type provided only with a fluid supply/removal path, a catheter of so-called double lumen type provided with another path for inserting a guide wire in addition to the fluid supply/removal path, a catheter of multi-lumen type provided with other passages for discharging medicine or for maintaining the blood flow between both sides of the balloon and the like are used. The structure of a balloon catheter of the invention can be applied to any of these balloon catheters.